How to Combine Two Animations with Different Y Locations
Let say you want animation A to go from point Y = 0 to Y = 1 from frame 0 to 19, and animation B to stay at point Y = 1 from frame 20 to 40.


You could parent your object to an empty that will stay still from 0 to 19, then at frame 20 move at Y = 1.
If you're talking about an armature, in Object mode, you could keyframe the object at frame 0 and 19, then at frame 20, keyframe it at Y = 1 so that it corrects the animation B location.
Again for an armature move animation B's root's location (+ 1 to Y location) or its bones locations (in the Graph Editor select the Y location curve and give it +1).
And you could do it with the Delta Transform values:


Open the Properties panel > Object > Transform > Delta Transform > Delta Location. You will tweak these values in order to change the object's 0 global location.

At frame 0 create a keyframe with X/Y/Z = 0/0/0. Duplicate this keyframe and put it at frame 19.

At frame 20 create a keyframe with X/Y/Z = 0/1/0.

When your object will arrive at frame 20, animation B begins and it should come back to 0, but the Delta Transform forces it to go to Y = 1. Therefore you won't see the object jump back to 0.



You can fix your particular case with the root's position. As you didn't change its position it would still make your armature position move whatever you do, so:


First your armature and animation are super messy, but let's ignore this. Find your root bone, you can find it in the Outliner, it's called b_C_Base, select it in the Outliner, switch your armature to Edit mode:





It's a very small bone so you can't see it, scale it. Now switch to Pose mode. You can see its position on the Z armature local position at frame 90, copy it.





Go to frame 116, when the animation is supposed to stop, you can see that the bone is set to back to its 0 position.





Paste the Z position you've copied, it will move the whole armature to the good position. Create a keyframe with i, it works.